Gun drill



March 27, 1956 J. FLElscl-IER 2,739,496

GUN DRILL Filed June 30, 1952 United States Patent GUN DRILL JohnFleischer, Royal Oak, Mich., assignor to National Twist Drill & ToolCompany, Rochester, Mich., a corporation of Michigan Application June30, 1952, Serial No. 296,426

1 Claim. (Cl. 7768) The invention relates generally to drills and refersmore particularly to improvements in relatively long drills commonlyknown as gun drills.

It is an object of this invention to provide a gun type drill whereinthe cutting edge, or edges, are carried by a tip which is not onlyformed separately from the shank but, in addition, is readily removablysecured to the shank of the drill.

As a result of the foregoing, manufacture and maintenance of the drillis greatly simplified. In practice the tips of the drills requireconsiderably more time to produce than the Shanks and in accordance withthis invention it is possible to produce the tips in their variousrequired sizes separately from the Shanks. Thus, it is practical for amanufacturer to maintain an inventory consisting of a number of tips ofdifferent sizes so that when a drill of standard Size is required it isonly necessary to make the comparatively simple shank. Also with thepresent invention, manufacturers may ship tips to users for installationon shanks in their possession. Hence, the tool cost is reduced becausethe user is not required to purchase a shank each time it is necessaryto replace a drill tip. Moreover when the cutting edges on the drill tipbecome worn to an extent requiring resharpening, the user in the matterof minutes may remove the tip from the shank. Thus sharpening of thecutting edges on the drill tip is greatly facilitated as it is muchsimpler to handle the relatively short drill tip than it is to handlethe complete drill.

It is still another object of this invention to provide a connectionbetween the shank and drill tip which is not only readily detachable butwhich assures a strong, rigid tie between the shank and drill tip. Thusall of the numerous advantages of a readily detachable connectionbetween the shank and drill tip are obtainable without sacrificingaccuracy.

The foregoing as well as other objects will become more apparent as thisdescription proceeds, especially when considered in connection with theaccompanying drawing, wherein:

Figure 1 is an elevational view of a drill embodying the features ofthis invention and showing the same in operative relation to aworkpiece;

Figure 2 is an end elevational view of the drill shown in Figure l;

Figure 3 is a cross sectional view taken on the line 3 3 of Figure l;

Figure 4 is a sectional View taken on the line 4-4 of Figure 3;

Figure 5 is a fragmentary perspective view of the inner end of the drillstern, and

Figure 6 is a fragmentary perspective view of the inner end of the drillbit or tip.

For the purpose of illustrating the present invention, l have selected agun type drill of considerable length comprising a shank or stem 10 anda bit or cutting tip 11. The stem 10 has a reduced part 12 at the outerend and the inner end is formed with a generally V-shaped recess 13having the opposite side walls 14 converging toward the axis of the stemand havingA a base 15. The base 15 extends substantially perpendicularto the axis of the stem and connects the radially inner edges of theside walls 14.

The bit or cutting tip 11 is fashioned with a projectionv 16 at theinner end having'opposite side walls 17 converging toward the axis ofthe cutting vtip and connected by an end wall 18 which extendsperpendicular to the axis of the cutting tip. The projection 16 on theinner end of the cutting tip 11 is fashioned to extend into the recess13 at the inner end of the stem 10. The walls 14 and 17 arepredeterminedly fashioned to respectively inti-` mately engage oneanother and form driving faces in is secured to the stem 10 by afastener element 19 having a head 20 and a threaded shank 21.

The fastener element 19 is insertable through a bore 22 extending forthe full length of the cutting tip 11' and, for reasons to be more fullyset forth, offset lat erally from the axis of the cutting tip 11. vThebore 22 is reduced at the inner end of the cutting tip 11 in order toprovide a shoulder 23 against which the head 20 on the fastener elementabuts. The reduced portion of the bore 22 opens through the wall 18 onthe projection 16 at the inner end of the cutting tip 11, and the stern10 is fashioned with an aligned bore 24 which is threaded.

The shank 21 of the fastener element 19 extendsr through the reducedportion of the bore' 22 and thread*` ably engages the bore 24. Theenlarged portion of the bore 22 is of ample diameter to freelyreceivethe head 20 on the fastener element 19 and to also receive a suitablesocket type wrench, not shown herein. present instance, the head 20 onthe fastener element has a. socket 26 which cooperates with the Wrenchto enable manipulating the fastener element 19. With the aboveconstruction, it will be noted that the fastener element 19 elfectivelyclamps the driving faces 14 and 17 together in a manner such that thefastener element is relieved of any driving stress. Although when thestem 10 of the drill is fastened to the cutting tip 11, the drillfunctions just as effectively as if it were made of one piece,

nevertheless, it will be apparent that the cutting tip 11 may be quicklyremoved from the stem by merely disengaging the fastener element 19.

By forming the cutting tip 11 separately from the stem 1l) and removablysecuring the two parts together,

numerous advantages are obtained. For example when the cutting tip 11requires sharpening it may be readily removed from the stem 10 andconsequently the sharpening operation is greatly simplilied. Also, whenthe cutting tip becomes worn to such an extent that it must bediscarded, replacement may be readily accomplished without replacing orreworking the stem 1t). Moreover,

the foregoing structure renders it possible for themanucircumferentially of the cutting tip 11 and extend in theV directionof length of the latter. The outer surfaces of the inserts 27 projectbeyond the outer surface of the cutting tip and are arranged on a circlehaving a diin the ameter greater than the. outside diameter of the stemI0. lt has been stated above that the aligned bores 22, 24 are offsetwith respect to the axis of the drill and the and cutting; tip, llrespectively. The groove; 30 extends for the full length of the cuttingtip' 11 and the; groove 29v has a length at least as great as the depthof?. t-he hole: to

be` drilled. i

The side wallsl of the chip. ute ZSLconx/ergc to a central opening orchannel 31 which extendsaxially through the cutting tip 11, and` stem10,. and coacts with anv inserted cutter 32 to form an undrilleclcenterrod 33 (Fig.v l) fromthe work beingy drilled for guiding the drillduring the Idrilling operation. In detail, the: cutter insert 32 islocated at the outer endv ofthe'tipll' and extends along one wall of thegroove 30' in the' tip 11. The insert 32 has a cutting-edge 34 at theradially outer edge thereof for cutting the hole in the workpieceand hasa cutting edge 35 at the radially inner edge thereof which. intersectsthe openingl to'forrn the'rod33. l

It will also be noted from the drawing that the stem A10 and cutting tip1l are formed with aligned passages 35. The passage 35 in. the tip 11extends for the full length thereof and suitable means isA provided forintroducing a coolant into the passage 35 at the outer end of the stem10. It will be noted from Figures 2 and 3 of the drawings that thepassage 35 is offset laterally from` both the openings 31 and alignedbores 22, 24 so as not to appreciably -Weaken the structure of thedrill.

It will be apparent from the foregoing that we have provided a gun typedrill havingl all of the desired structural features and at the sametime renderingit possible to quickly detachably secure the cutting tipto the stem. The detachable mounting is of a nature that it does notinterfereV with the chip flute 28, opening 31 for producing the drillguiding rod 33, and the coolant passage 35.

What I- claim as my invention is:

A drill having an elongatedstem. part, a separable cutting tip partaligned with said stem part' in end-to-end relation, one of said partshaving a generally V-shaped recess extending entirely across the innerend thereof, the converging sides of said recess being symmetricallyarranged relative to the drill axis to provide driving faces, aprojection on the inner end of the other part received in said recess,said projection having converging sides arranged symmetricallyI relativeto the drill axis to provide driving faces disposed. to have intimatesurfaceto-surface engagement with the driving faces` ofsaid recess,thereby to alignsaid parts and to provide a driving' connectiontherebetween, the tip' of said projection being spaced from the base ofsaid recess in order not to interfere withclamping the. driving. facesof said" parts `in intimate surface-to-surface engagemenh, a first borein said cutting tip part extending from one end thereof to the other andhaving a shoulder adjacent the inner end of said cutting tip part, asecond bore in said stem part aligned with the rst bore andY beinginternallythreaded, a fastener elementffor removably connecting saidvparts and for clamping said driving faces inintimate surfaceto-surfaceengagement, said` fastener element having a head seated against saidshoulder andl havingia threaded shank threadedlyengaged with thesecondbore, said bores being` laterally offset from the drill axis, a groovein said cutting tip part providing a chip flute extending the full!,length thereof, a groove in said stem part pro viding al chipV fluteextending lengthwise thereof in continuation of4 the chip ute inJ saidcutting, tip part, and

aligned central channels in said parts extending along.

the axis of said drill-,and communicating with therespectiveA chip utes.

References Cited in they file of this patent UNITEDl STATES PATENTS1,461',462 Smith et al. July 1D, l92'3` 1,746,716 Sasse Feb. 1l, 19302,325,535 Nordberg July 27, 1943 2,418,021" Fleischer Mar. 25, 1947

